This is something we are working on. Best way to help us get there is test the OSS version we've released and give us your feedback. We'll be releasing some new nightly builds soon and we encourage Mac users to help us test. We don't have an official date as we'd like to make sure the quality is there prior to releasing this.

Looking for new beta users -> Co-Founder of Acompli. Previously worked at Zimbra (and Yahoo! & VMware) since 2005.